Lamp and light-sensitive cell housing



NOV. 19, 1968 MlLLER ETAL 3,412,257

LAMP AND LIGHT-SENSITIVE cum, HOUSING 5 She ets-Sheet 1 Original FiledFeb. 26, 1965 SWITCH SWITCH INVENTORB ROBERT E MILLER JOHAN LUND ATTOBNEY Nov. 19, 1968 R. F. MILLER T LAMP AND LIGHT-SENSITIVE CELL HOUSING 5Sheets-Sheet 2 Original Filed. Feb. 26, 1965 MOTOR -SWITCH .SELFTAFPING- scams 5! BU]. B AND 5OCKET INJECTION MOLDED LIGHT AND CELLHOUSING RESISTOR ASSEMBLY INVENTORfi Roszm F. rmuafi JOHAN LUND THER HALPROTECTOR SWITCH ATTORNEY Nov. 19, 1968 R. F. MILLER ET AL 3,412,257

LAMP AND LIGHT-SENSITIVE CELL HOUSING Original Filed Feb. 25, 1965 5Sheets-Sheet 3 SWITCH SWITCH INVENTORS ROBERT F. MILLER JOHAN LUNDATTORNEY Nov. 19, 1968 R ETAL 3,412,257

LAMP AND LIGHT-SENSITIVE CELL HOUSING Original Filed Feb. 25, 1965 5SheetsSheet 4 START M Q m? MOTOR "*1 $11.2 noron? jar. P10TOR#3 THERMALPROTECTOR SWITCH SET 'N THERMAL canam INVENTORB ROBERT F. MILLER JOHA'NLUND BY/MXM/ ATTORNEY Nov. 19, 1968 R. F. MILLER ETAI- LAMP ANDLIEEHT-SENSITIVE CELL HOUSING Original Filed Feb. 26, 1965 EXPECTED$PREAO QA zevncm Hen-l Q 0 0 V v 91 0 G708 SQOHJV ca J 2 2 $5 & -0 mg i0 u c 0 '2' Q 4 3 ems ssouav u g 9 evuon M01 5 Sheets-Sheet 5 6 8 m E AcVOLTS INVENTOR5 ROBERT F. MILLER JOHAN LUND ATTORNEY United StatesPatent Office 3,412,25 7 Patented Nov. 19, 1968 3,412,257 LAMP ANDLIGHT-SENSITIVE CELL HOUSING Robert F. Miller and Johan Lund, Kokomo,Ind., assignors to General Motors Corporation, Detroit, Mich., acorporation of Delaware Original application Feb. 26, 1965, Ser. No.435,663, now Patent No. 3,320,505, dated May 16, 1967. Divided and thisapplication Feb. 20, 1967, Ser. No. 617,175

3 Claims. (Cl. 250239) ABSTRACT OF THE DISCLOSURE This specificationdiscloses two embodiments of a switching structure housing. In oneembodiment, an end plate and an injection molded light and cell housingare tightly secured to opposite sides of a magnetic inductor core memberhaving a tapped winding thereon to form a unitary assembly. In the otherembodiment, the structure comprises a U-shaped body portion having apair of enlarged side segments and corresponding U-shaped grooving alongopposite edges. A pair of side walls are dovetail fit into thecorresponding U-shaped grooves and a cover is secured to the enlargedside segments to form a unitary enclosure.

This application is a division of application Ser. No. 435,663, filedFeb. 26, 1965, now United States Patent No. 3,320,505 which issued May16, 1967.

This invention relates to utilization of solid state devices, and, moreparticularly, to circuitry for opto-electronic control of machineoperation for conditions of starting and running.

Problems of contact wear and communications interference are encounteredduring transition from starting to running operation of a motor meansfor example. Attempts have been made to overcome such problems.Accordingly an object of the present invention is to provide new andimproved opto-electronic control arrangement for machine starting andrunning operations with increased reliability because of removal ofwearing contact means accompanied by smooth and quiet transition fromstart to run and vice versa with a combination of components utilizingsolid state devices which are light sensitive.

Another object of this invention is to provide dynamoelectric machinemeans having winding portions thereof usable for starting and runningpurposes subject to light energization in response to magnitude ofstarting and/ or running current conditions whereby solid statephoto-sensitive switching establishes machine winding portions utilization.

Another object of this invention is to provide optoelectronic motorstarting with a light-triggered solid state switching and with impedancemeans adapted to function regardless of variously sized motor means.

A further object of this invention is to provide optoelectronicswitching components in combination to establish motor starting andrunning connection of winding portions having motor speed and/ orcurrent sensing means for light energization in accordance therewithadjacent to parallel photoconductive cells of which resistance changesnon-linearly effectively to make and break starting connections. I

Another object of this invention is to provide on hermetically sealedmotor means such as refrigeration equipment a motor starting controlwith opto-electronic switching components including at least one lightactuated silicon control rectifier means and an impedance meansmagnetically responsive to motor operating conditions whereby problemsof contact wear and communications interference are overcome withsuccessful operation under various circumstances.

Further objects and advantages will be apparent from the followingdescription, reference being had to the accompanying drawings whereinpreferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 shows motor starting circuitry having features in accordancewith the present invention.

FIGURE 2 shows motor starting circuitry for further starting arrangementfor motor means including overload protection.

FIGURE 3 illustrates application of features of the present invention toanother motor means.

FIGURE 4 illustrates circuitry with tapped impedance means and motorstarting components having features in accordance with the presentinvention.

FIGURE 5 is an exploded perspective view of structural components forcircuitry of FIGURE 4.

FIGURE 6 illustrates circuitry with tapped motor winding and startingcomponents in accordance with the present invention.

FIGURE 7 shows circuitry including overload protector and startingcomponents with tapped motor winding means for operation also inaccordance with the present invention.

FIGURE 8 shows modifications of circuitry in FIG- URES 6 and 7.

FIGURE 9 is an exploded perspective view of structural components forcircuitry of FIGURES 6, 7 and 8.

FIGURE 10 is a graphical showing of component characteristics as anexample of operation in accordance with the present invention.

In FIGURE 1 there is shown circuitry including first and second powersupply lines 11 and 12 for energization of a motor means having asquirrel cage rotor 13 as well as a starting of phase winding portion 14and running or main winding portion 15. A transformer means including aprimary portion 16 in series from the supply line 11 to the runningwinding 15 is magnetically coupled with a secondary transformer portion17 for energization of a neon bulb or gas bulb light means 18. Asuitable limiting resistance means 19 can be provided in series betweenthe transformer secondary portion 17 and bulb means 18. The bulb means18 having the gaseous filling is caused to fire or become illuminatedbecause in response to relatively large or high currents in the runningwinding portion 15 and primary transformer portion 16 during starting,the current transformer secondary portion provides signals of sufficientstrength for voltage and current values to fire the bulb means. Firingor illumination of the bulb means 18 occurs in proximity to or adjacentto a light-controlled silicon controlled rectifier means or cadmiumsulfide cell that is a light dependent resistor means 20 in FIGURE 1. Itis to be understood that the motor means including the rotor 13,starting winding portion 14 and running winding portions 15 can beinstalled on a hermetically sealed refrigeration compressor means suchas on an air conditioning or refrigerator means. Use of the lightcontrolled silicon controlled rectifier means or light dependentresistor means 20 permits elimination of movable contacts and insuresreliability as Well as long life. FIGURE 1 illustrates use of such lightsensitive means 20 together with a current detection in the main orrunning winding portion of the motor. At high starting currents thecurrent transformer puts out enough voltage for firing the bulb means 18which turns on the starting winding due to sensing of the light from thebulb means 18 in the light sensitive means 20. As running speed isreached, the current magnitude in the running winding portion decreasessuch that minimum potential for sustaining bulb firing is passed. It isto be noted that hysteresis characteristics of the gas bulb or tubemeans 18 are ideally utilized for causing the starting winding to cut inbelow the cutout point in terms of motor speed yet requiring no movablecontacts or centrifugal switch devices.

During functioning of the circuitry of FIGURE 1, the transformer withits primary Winding portion 16 inserted in series with the main motorwinding portion provides a secondary voltage due to turn-on motorwattage whereby inrush current is sufficient to light the bulb means 18.The light of the bulb means 18 then lowers the resistance of the lightdependent resistor means, cadmium sulfide cell or light controlledsilicon controlled rectifier means so that the phase or starting winding14 is energized.

FIGURE 2 shows motor starting circuitry for further starting arrangementfor motor operation from a suitable source of energy connected to asupply line 21 and a supply line 22. The motor means includes a rotorportion 23 as well as a phase or starting winding portion 24 and a mainor running Winding portion 25 suitably enclosed in a housing or hermeticunit as represented by dotted lines in FIGURE 2. A pair of lightdependent resistor means or cadmium sulfide cells 26 and 27 are inparallel with each other though collectively in series with the startingwinding 24 of the motor means. In circuitry of FIGURE 2, an iron-coreinductor means 28 is connected in series with the main or runningwinding 25 of the motor for sensing the inrush current at turnon. Thevoltage induced across the inductor means 28 is applied to a seriescombination of a resistor 28r and an incandescent lamp bulb means 29.The bulb means 29 receives rated voltage during this initial condition.The light from the bulb means falls on two cadmium sulfidephotoconductive cells identified previously by reference numerals 26 and27 so as to lower their parallel resistance sufficiently to allow thestarting winding portion 24 to draw current.

The motor means starts when the light from the bulb means 29 lowersparallel resistance of the cadmium sulfide photoconductive cells 26 and27. As the speed of the motor means increases, the current through themain winding portion 25 decreases to its normal operating value with aconsequent drop in the inductor voltage. The bulb and resistancecombination are sufficiently non-linear that the bulb extinguishes, forall practical purposes, and the photoconductive cells 26 and 27 assume adark resistance value sufficient to open-circuit the starting windingportion 24. A suitable thermal protective means or relay 30 can beprovided in series with the supply line 22 and the other componentsenergizable together with the main winding portion 25 as shown in'FIGURE 2. Some of the advantages of this circuitry are increasedreliability because of removal of contacts, a smooth and quitetransition from starting to running operation since the starting currentis inversely proportional to speed, and the use of a resistive switchthat virtually eliminates radio interference during switching operation.

Circuitry of FIGURE 3 is similar to that of FIGURE 2 with power beingsupplied by way of lines 31 and 32 for energization of a motor meanshaving a rotor 33 as well as a phase or starting winding 34 and main orrunning winding 35. An iron-core inductor means, resistance means andlamp bul'b means as well as cadmium sulfide photoconductive cells arerepresented by reference numerals ten digits higher than those for thecircuitry of FIGURE 2. Thus the photoconductive cells 36 and 37 areprovided in the circuitry of FIGURE 3 and are connected in series withthe starting winding also having a capacitance or phase shifting means40 in series therewith. The motor means and switch means collectivelyincluding certain of the components identified by reference numeralswith the digits ten numerals higher than in FIGURE 2 are indicated andadapted for use particularly with horsepower motor means onrefrigerators of a type made by the assignee of the present invention.It is to be noted that the iron-core inductor means 28 and 38 can bemodified to have at least one or more tap connections thereto as 4represented in the circuitry illustrated by FIGURE 4 of the drawings.

In FIGURE 4 of the drawings the circuitry is energized by supply lines41 and 42 subject to inclusion of a switch means 42s. The motor meansincludes a suitably journalled rotor 43 as well as a starting windingportion 44 and running winding portion 45. The cadmium sulfidephotoconductive cell means 46 and 47 are connected in series with acapacitance means as to the starting winding portion 44 in a mannersimilar to that noted for circuitry of FIGURE 3. The iron-core inductormeans 48 in the circuitry of FIGURE 4 has an end connection 48a as wellas tap connections 48b and 48c selectively engageable by a movableswitch arm 48s connected to a juncture 48j to which a resistance means48r is connected in series from the energizable neon or lamp bulb means49. In the circuitry of FIGURE 4, various hermetic refrigeration motormeans having sizes or ratings exemplified by 1 horsepower, /6 horsepowerand A; horsepower can be accommodated. Connection of the switch arm 48sto the end connection 48a of the iron-core inductor means 48 utilizesthe full inductor winding for A; horsepower rating motor operation.Similarly, movement of the switch arm 48s to the central or intermediatetap connection 48b permits operation of a A, horsepower hermetic motormeans whereas movement of the switch arm 48s into engagement with thetap connection 48c permits operation of a V horsepower hermetic motorsize though having the same "basic solid state motor starting switcharrangement previously described. It is to be noted that for thecircuitry of FIGURE 4 there can be certain motor ratings such as A2horsepower for example which would not require a starting capacitor suchas indicated by reference numeral 50 and then the connection of thecadmium sulfide photoconductive cells 46 and 47 in parallel with eachother can be made in series directly to the starting winding portion 44.

In addition to the advantages noted previously for circuitry of FIGURE 1for example, it is to be understood that an additional advantage isobtainable in the circuitry of FIGURE 4 because the tapped inductormeans 48 is used to provide a universal switching operation which can beutilized for starting of various motors of widely differing sizes. Stilla further advantage occurs in the event of a catastrophic failure ofstarting switches for which a comparison can be readily made. Inexisting mechanical switches, one possible mode of failure is for theswitch to stay on resulting in a burned out starting winding. In thecase of a photoconductive switching operation, the only failure mode dueto excessive overloads is to burn the cells or light controlled meansclear thus resulting in protection of the starting winding of the motormeans.

FIGURE 5 illustrates in a perspective exploded view a tapped inductorand switch means assembly which can provide the starting features forrefrigeration motors to be operated in accordance with the presentinvention. The assembly is generally indicated by numeral 51 to includethe following components. There is an end plate or base portion 52having a central offset 53 as well .as corner apertures 54 through whichself-tapping screw means 55 can be inserted to complement a magneticcore or inductor means 56 carrying a coil 58 therewith. The coil 58 canhave an end connection 58a as well as tap connection 58b and further tapconnection 58c comparable to the inductor coil and connectionsidentified for circuitry of FIGURE 4 by numerals having ten digits belowthose in FIGURE 5. The wound coil 58 is adapted to be mounted against anoutwardly extending flange 59 of an end cover or housing portion 60 inwhich a resistance means 58r is carried. The leads including the tapconnections to the coil can be joined to suitable screws or terminalpoints on this housing 60 for external connection in accordance with thecircuitry of FIGURE 4 for example. The housing 60 includes aperturing 61on each of opposite sides thereof together with screw mounting holes 62to receive a heat sink portion 63 carrying the photo-conductive cells 66and 67 comparable to the cells or light controlled devices 46 and 47 inthe circuitry of FIGURE 4. A lamp bulb means 69 mounted in a socketassembly 70 on the housing 60 with a suitable energizing lead theretocan be provided in a location intermediate the light controlled means 66.and 67. The housing 60 can be made of a suitable plastic materialmolded to a predetermined configuration. The resistance means 58r canhave a value of ohms plus or minus 5% with five watt rating for exampleand the lamp bulb means 69 can be rated for 6.3 volts or other suitablevoltage. A thermal protector switch or overload device 68 can also bemounted within the housing 60 if provided in circuitry previouslydescribed for FIGURE 2 and subsequently noted with description forFIGURES 6, 7 and 8 for example.

Circuitry of FIGURE 6 provides a refinement of the features previouslydescribed though eliminating cost of certain components while retainingfunction thereof where possible. Thus in both FIGURES 6 and 7 theiron-core inductor means is eliminated. Also only one light controlledcell or device and heat sink assembly can be provided. Circuitry ofFIGURE 6 requires a single cadmium sulfide photoconductive cell means ofincreased power handling capacity and the features of this circuitarrangement can be summarized to include the following. Power supplylines 71 and 72 can be connected to a suitable source. A motor meanshaving a suitably journalled rotor portion 73 as well as a phase orstart winding 74 and main or run winding 75 can be provided subject to atap connection 7ST on the main winding portion 75. A lamp bulb means isprovided in a location adjacent to one side of a heavy dutyphotoconductive cell means 76. A thermal protection switch or overloadmeans 77 can be provided in the supply line 72 as shown in FIGURE 6. Anon-linear solid state device 78 can be used in place of resistancemeans previously noted. The lamp bulb means designated by referencenumeral 79 can be in series with this non-linear solid state device toinsure that the light bulb means 79 is off during running operation andstrongly on during starting operation. The light con trolled switchingoperation can be adapted to occur with sufficient powerance so thatconsiderable variations in motor fabrication including airgap-windingsand the like would have no effect on the switching operation.

Another motor means generally indicated by numeral 80 in FIGURE 7 canhave supply lines 81 and 82 therewith for energization from a suitablesource. The motor means can include a rotor portion 83 suitablyjournalled as well as a phase or starting winding portion 84 and a mainor running winding portion 85 having a tap connection 8ST thereto. Apair of cadmium sulfide photoconductive cells or :light controlledsemi-conductor means 86 and 87 can be provided in parallel with eachother though series connected as to the start winding portion 84. Asuitable thermal protective switching means 88 can be provided as shownin FIGURE 7 together with a lamp bulb means 89 and resistance means891'. The circuitry of FIGURE 7 also eliminates the inductor meansseparately by providing an internal inductor in the run winding to takethe place of'the external inductor. It is to be understood that the mainwinding portion 85 is located in the magnetic stator core in such a waythat a different magnetic path exists for the main winding portion andinternal inductor. Thus the tap connection 8ST as well as 75T is not perse a simple tap but rather provides a different magnetic path for thetapped portion. This is necessary "because the tapped winding mustundergo a larger voltage drop than the remainder of the running windingunder conditions of current inrush. The tap voltage is to be roughlylinear with current. One way 'of accomplishing this characteristic is touse ferrous wedges in the stator slots surrounding the tap coil portion.Such an approach is particularly useful if unused or dead slots alreadyexist in the motor arrangement. It is to be understood that apredetermined tap connection can be provided for each of severaldiffering motor sizes designated accordingly on the plastic housingassociated therewith. By use of several tap positions with a particularcoil arrangement it is possible for a single light controlled switcharrangement to handle various requirements.

FIGURE 8 of the drawings illustrates circuitry for operation of themotor (not shown) to be energized from a pair of supply lines in amanner previously identified of which only one line 92 is shown in thisview. An external tapped inductor means 93 is provided havingconnections 93a, 93b and 930 therewith adapted to fit various motorsizes as designated in FIGURE 8. A starting connection 94 can beprovided with a pair of cadmium sulfide photoconductive cells or lightcontrolled semi-conductor devices 95 and 96 in parallel with each otherthough included in series with this starting connection 94. A thermalprotective relay means or overload protector device 97 can be providedas shown as well as a resistance means 98 and a lamp bulb means 99. Thearrangement of FIGURE 8 permits a manufacturer or service man to connectthe starting switch arrangement including the tapped inductor to aproper motor size connection and the bulb 99 has a lead or connection990 therewith optionally joined to the appropriate tap corresponding tothe motor size. Physical arrangement of the switching structure ofFIGURE 8 would correspond substantially to that shown in FIGURE 5 of thedrawings. The structure of FIGURE 5 provides for an external coil orinductance means to be suitably tapped for connection to motors ofdifferent sizes.

It is to be understood that the circuit arrangement of FIGURES 6 and 7would not require any external tapped inductance means and therefore adiffering physical arrangement illustrated by FIGURE 9 of the drawingscan be utilized for the switching components. The switching meansgenerally indicated by numeral 101 in FIGURE 9 includes a substantiallyU-shaped body portion or support 102 having a pair of enlarged sidesegments 103 to which fastening devices such as screws 104 can bethreaded to hold a cover or plate 105 thereto. Prior to installation ofthe cover or plate 105 a pair of opposite sidewalls 106 can be fittedwith a dovetail fit along flanging 107 thereof complementary tosubstantially U-shaped grooving 108 in the support or body portion 102.Each of the sidewalls 106 can be provided with suitable aperturing forinstallation of a copper heat sink portion 109 as well as a pair oflight controlled or photoconductive cell devices designated by referencenumeral 110 in FIG- URE 9 though corresponding to similar devicesidentified by differing reference numerals in other views of thedrawings. These cells 110 can be suitably connected in parallel to eachother. A socket means 111 having a lamp bulb means 112 suitably joinedby a lead connection 114 thereto for energization of the lamp bulb canbe provided as previously described. This lamp bulb and socketarrangement is located structurally in a location intermediate theparallel-connected cells 110. A resistance means 115 and an overload orthermal protector switch set in thermal cement and indicated by numeral116 can also be mounted internally on the support or body portion 102.

It is to be understood that the housing 60 in FIGURE 5 and body portionor support 102 in FIGURE 9 are made of a light-tight molded assembly ofthe bulb and cells therewith. Use of a non-linear device 78 for examplein series with the lamp bulb 79 in circuitry of FIGURE 6 can include anepoxy or coated P-N-P germanium device alloyed with :leads in one shoton a low resistivity base of poor lifetime. The result would be aback-to-back zener regulator with a breakover voltage of about two orthree volts. The device would be fairly temperature insensitive becauseof the doping, at least more so than the cadmium sulfide cells. Use ofsuch a non-linear device will permit a reduction in inductor size ofabout forty percent. The specific motor protection means per se dependsupon the power rating of the motor and temperature control of aparticular refrigeration installation.

FIGURE of the drawings provides a graphical showing of componentcharacteristics as an example of operation in accordance with thepresent invention. The systems and arrangements described in thisdisclosure concern the general concept of using a current controlledlight source to trigger a solid state device to act as a switch forenergizing and de-energizing the starting winding of an alternatingcurrent motor. A light bulb actuated by a nonlinear inductor and aphotoconductive cell as the light actuated starting winding switch canprovide circuit reliability and proper heat dissipation. Since movingparts are avoided there is a minimum of wear resulting from on-offoperation of the starting arrangement. It has been found that the lampbulbs 1ast well over one million cycles and more particularly in a rangebetween 1.3 and 1.9 million cycles. Based upon a refrigerator startingevery ten minutes for a twenty-four hour day this would extrapolate to alife of about twenty-two years. Use of the heat sink for adequatecooling assures reliability of the light control cells or devices forsubstantially the same time cycle. It is to be noted that if anon-linear device (P -N-P germanium) is used in series with the lamp,the inductor can be replaced by a resistor or capacitor means. Thisfurther simplifies construction and is more economical. Also, the heavyduty cell means 76 in FIG- DRE 6 can be replaced by two four-layertwo-terminal controlled rectifier structures connected in parallel withalternate polarity and triggered by light. Such an arrangement isslightly more expensive but will handle heavier currents. Also the heavyduty cell can be replaced by a five-layer, four junction single crystalsilicon device which acts as a symmetrical A.C. switch and is triggeredby light. Also the pair of photoconductive cells can be used to bias apair of silicon controlled rectifiers which switch the windingconnections. Furthermore, a photoconductive cell can he used to bias afour-terminal five-layer, four junction A.C. switch for switching thestarting winding on and off. Thus, for switching, not only a lightcontrolled silicon controlled rectifier means or specific four-layerdevice generally with three terminals can be used but also lightcontrolled or light triggered four and five layer P-N junction devicescan be used.

'11: summary, the present disclosure provides a method of switching astarting winding of a split phase motor by means of an optical switchwith a light trigger actuated by the motor current demand. Also thecircuitry illustrated for the present invention permits use of aninductance as a means of converting current demand to a light input.Also features of the present invention make it possible to use anon-linear inductor with an air gap to achieve full on-oif operation ofa lamp bulb. Operating characteristics as represented in FIGURE 10graphically involve use of a light bulb non-linear inductor andresistance means in combination to achieve complete on-off :lightoperation to control starting and running of a motor means. A nonlinearresistor is disclosed in US. Patent 3,162,831-

Heath issued December 22, 1964. Also the switching operation can beaccomplished by use of paralleled cadmium sulfide cells as lightdependent resistors. The tapped inductor means can accommodate startingand running operation for differing sizes of motors. The structuralarrangement of FIGURE 5 provides a practical mounting and assembly ofthe components together with a transformer or inductor means. The lightsensing means can be dependent upon the main winding current. Also theinductor can be provided internally of the motor .frame as a modifiedportion of the main winding of the motor means. A non-linear elementsuch as the three layer P+-N-P+ low voltage germanium device can be usedin series with the light source.

Features of the present invention further make it possible for a lightactuated pair of silicon controlled rectifiers to be used as a switch inthe starting winding of a motor means. The starting winding can beswitched for energization using a light actuated P-N-P-N-P or N-P-N-P-Nsingle crystal device. A single light or lamp bulb means is used totrigger a pair of photoconductive cells each controlling a siliconcontrolled rectifier means (one for each half of the A.C. cycle), to actas a starting winding switch. Also one light or lamp means can trigger aphotoconductive cell which turns on a symmetrical five layer controlledrectifier in the starting winding. Furthermore, a resistor can be usedto replace the inductor in the light sensor or a capacitor can be usedin place of the comductor in the light sensor where non-linear devicesare provided in series with the lamp means.

While the embodiments of the present invention herein disclosedconstitute preferred forms, it is to be understood that other formsmight be adopted.

What is claimed is:

1. Physical arrangement of switching structure of the class disclosed,comprising, a substantially U-shaped body portion having a pair ofenlarged side segments and corresponding U-shaped grooving alongopposite edges, a pair of dovetail-fit sidewalls each complementary tosaid grooving and each centrally apertured, a lamp bulb and socket meanscentrally supported by said U-shaped body portion, and heat-sink-mountedlight sensitive cell means secured to each of said sidewalls.

2. The arrangement of claim 1 wherein said Ushaped body portion hasthermal protector means and resistive impedance means mounted inlocations internal adjacent to said enlarged side segments.

3. The arrangement of claim 2 wherein said U-shaped body portion has acover secured thereto as said enlarged side segments.

References Cited UNITED STATES PATENTS 2,457,023 12/1948 Zelt 174502,574,783 11/1951 Hedding et al 317-99 X 3,289,002 11/ 1966 Goodman250-239 X 3,136,932 6/ 1964 Trent 317-234 ROBERT SEGAL, PrimaryExaminer.

